U.S. patent number 9,719,691 [Application Number 14/351,428] was granted by the patent office on 2017-08-01 for air-conditioning apparatus.
This patent grant is currently assigned to Mitsubishi Electric Corporation. The grantee listed for this patent is Osamu Morimoto, Daisuke Shimamoto, Naofumi Takenaka, Shinichi Wakamoto. Invention is credited to Osamu Morimoto, Daisuke Shimamoto, Naofumi Takenaka, Shinichi Wakamoto.
United States Patent |
9,719,691 |
Takenaka , et al. |
August 1, 2017 |
Air-conditioning apparatus
Abstract
When indoor units are performing a cooling operation, an
air-conditioning apparatus controls four flow passage switching
valves, for example a first solenoid valve, a second solenoid
valve, a third solenoid valve, and a fourth solenoid valve, so that
a number of intermediate heat exchangers operating as evaporators
is greater than in a cooling main operation. During the cooling
main operation, a target value for suction pressure or evaporating
temperature at a compressor is set equal to or lower than that in a
case in which the indoor units are performing the cooling
operation, and a frequency of the compressor and a capacity of a
heat-source-side heat exchanger are controlled.
Inventors: |
Takenaka; Naofumi (Chiyoda-ku,
JP), Wakamoto; Shinichi (Chiyoda-ku, JP),
Morimoto; Osamu (Chiyoda-ku, JP), Shimamoto;
Daisuke (Chiyoda-ku, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Takenaka; Naofumi
Wakamoto; Shinichi
Morimoto; Osamu
Shimamoto; Daisuke |
Chiyoda-ku
Chiyoda-ku
Chiyoda-ku
Chiyoda-ku |
N/A
N/A
N/A
N/A |
JP
JP
JP
JP |
|
|
Assignee: |
Mitsubishi Electric Corporation
(Tokyo, JP)
|
Family
ID: |
48745031 |
Appl.
No.: |
14/351,428 |
Filed: |
January 5, 2012 |
PCT
Filed: |
January 05, 2012 |
PCT No.: |
PCT/JP2012/000041 |
371(c)(1),(2),(4) Date: |
April 11, 2014 |
PCT
Pub. No.: |
WO2013/102953 |
PCT
Pub. Date: |
July 11, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20140260387 A1 |
Sep 18, 2014 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B
13/00 (20130101); F24F 3/065 (20130101); F24F
11/72 (20180101); F24F 11/83 (20180101); F25B
2313/003 (20130101); F25B 2313/0231 (20130101); Y02B
30/741 (20130101); Y02B 30/70 (20130101); F25B
25/005 (20130101); F25B 2313/0272 (20130101); F25B
2600/0253 (20130101) |
Current International
Class: |
F24F
11/02 (20060101); F25B 13/00 (20060101); F24F
11/00 (20060101); F24F 3/06 (20060101); F25B
25/00 (20060101) |
Field of
Search: |
;60/228.4
;62/181,183,159 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102016450 |
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Apr 2011 |
|
CN |
|
4-6374 |
|
Jan 1992 |
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JP |
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5-10619 |
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Jan 1993 |
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JP |
|
2007-147203 |
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Jun 2007 |
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JP |
|
2010/050003 |
|
May 2010 |
|
WO |
|
2010/050006 |
|
May 2010 |
|
WO |
|
WO 2010/050000 |
|
May 2010 |
|
WO |
|
WO 2010050000 |
|
May 2010 |
|
WO |
|
WO 2010/131378 |
|
Nov 2010 |
|
WO |
|
WO 2010131378 |
|
Nov 2010 |
|
WO |
|
WO 2011052040 |
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May 2011 |
|
WO |
|
2011/080805 |
|
Jul 2011 |
|
WO |
|
2011/089637 |
|
Jul 2011 |
|
WO |
|
Other References
Nelson, Eric, "Refrigeration Basics 101", Jun. 5, 2010. cited by
examiner .
International Search Report issued Apr. 17, 2012, in
PCT/JP12/000041 filed Jan. 5, 2012. cited by applicant .
Combined Chinese Office Action and Search Report issued Dec. 30,
2015 in Patent Application No. 201280059769.X (with English
language translation and English translation of categories of cited
documents). cited by applicant .
Extended European Search Report issued on Sep. 15, 2015 in European
Patent Application No. 12864165.1. cited by applicant.
|
Primary Examiner: Jules; Frantz
Assistant Examiner: Sanks; Schyler S
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
The invention claimed is:
1. An air-conditioning apparatus comprising: a heat source unit
including a compressor, a first flow passage switching valve that
switches a flow passage of a first refrigerant, wherein the heat
source unit also includes a heat-source-side heat exchanger; a
plurality of indoor units each including a use-side heat exchanger;
a relay unit including a plurality of intermediate heat exchangers
each of which is operable in either a condenser mode or an
evaporator mode, second flow passage switching valves that switch
operation of the indoor units between heating and cooling, and
third flow passage switching valves that switch connection of the
intermediate heat exchangers between the condenser mode and the
evaporator mode, the air-conditioning apparatus including a
primary-side cycle through which a primary-side heat transfer
medium circulates between the heat source unit and the relay unit,
and a secondary-side cycle through which a secondary-side heat
transfer medium circulates between the relay unit and the indoor
units, wherein heat exchange is performed between the primary-side
cycle and the secondary-side cycle in the intermediate heat
exchangers, wherein when all of operating indoor units out of the
plurality of indoor units are performing a cooling operation, the
third flow passage switching valves are controlled such that the
number of the intermediate heat exchangers operating as evaporators
is greater than in a cooling main operation in which, out of said
plurality of indoor units, an indoor unit performing cooling and an
indoor unit performing heating exist at the same time and the first
flow passage switching valve is controlled so that the
heat-source-side heat exchanger operates by being connected to a
discharge side of the compressor; and control means for controlling
a frequency of the compressor and a capacity of the
heat-source-side heat exchanger such that, during the cooling main
operation, a target value for a suction pressure or an evaporating
temperature at the compressor is set lower than the target value
for the suction pressure or the evaporating temperature at the
compressor in a case where all of the operating indoor units are
performing the cooling operation.
2. The air-conditioning apparatus of claim 1, wherein a difference
in a load capacity between cooling and heating modes of the indoor
units is different from a difference in a heat exchange capacity
between cooling and heating modes of the intermediate heat
exchangers.
3. The air-conditioning apparatus of claim 1, wherein the number of
the indoor units connected to the relay unit is greater than the
number of the intermediate heat exchangers.
4. The air-conditioning apparatus of claim 1, wherein the target
value for the suction pressure or the evaporating temperature in
the cooling main operation is determined based on the target value
for the suction pressure or the evaporating temperature when all of
the operating indoor units are performing the cooling operation,
capacities of the intermediate heat exchangers, and heat exchange
capacities of the indoor units performing the cooling
operation.
5. The air-conditioning apparatus of claim 1, wherein the target
value for the suction pressure, a discharge pressure, the
evaporating temperature, or a condensing temperature in the cooling
main operation is set based on an output value of a pump that
drives the secondary-side heat transfer medium in the
secondary-side cycle.
6. The air-conditioning apparatus of claim 1, wherein a control
target value for the secondary-side cycle is set in accordance with
heat exchange capacities and operation modes of the indoor units,
and a control target value for the primary-side cycle is set to be
equivalent to the control target value for the secondary-side
cycle.
7. The air-conditioning apparatus of claim 1, wherein both in a
case where at least one of the intermediate heat exchangers
operates as an evaporator and in a case where at least one of the
intermediate heat exchangers operates as a condenser, a flow of the
secondary-side heat transfer medium is operable so that a flow of
the primary-side heat transfer medium and the flow of the
secondary-side heat transfer medium are opposed to each other.
8. The air-conditioning apparatus of claim 1, wherein the
intermediate heat exchangers have different heat transfer areas,
and the intermediate heat exchangers serve as evaporators or
condensers in accordance with a heat exchange capacity and an
operation mode.
9. An air-conditioning apparatus comprising: a heat source unit
including a compressor, a first flow passage switching valve that
switches a flow passage of a first refrigerant, wherein the heat
source unit also includes a heat-source-side heat exchanger; a
plurality of indoor units each including a use-side heat exchanger;
and a relay unit including a plurality of intermediate heat
exchangers each of which is operable in either a condenser mode or
an evaporator mode, second flow passage switching valves that
switch operation of the indoor units between heating and cooling,
and third flow passage switching valves that switch connection of
the intermediate heat exchangers between the condenser mode and the
evaporator mode, the air-conditioning apparatus including a
primary-side cycle through which a primary-side heat transfer
medium circulates between the heat source unit and the relay unit,
and a secondary-side cycle through which a secondary-side heat
transfer medium circulates between the relay unit and the indoor
units, wherein heat exchange is performed between the primary-side
cycle and the secondary-side cycle in the intermediate heat
exchangers, wherein when all of operating indoor units out of the
plurality of indoor units are performing a heating operation, the
third flow passage switching valves are controlled such that the
number of the intermediate heat exchangers operating as condensers
is greater than in a heating main operation in which, out of said
plurality of indoor units, an indoor unit performing cooling and an
indoor unit performing heating exist at the same time and the first
flow passage switching valve is controlled so that the
heat-source-side heat exchanger operates by being connected to a
suction side of the compressor; and control means for controlling a
frequency of the compressor and a capacity of the heat-source-side
heat exchanger such that, during the heating main operation, a
target value for a discharge pressure or a condensing temperature
at the compressor is set higher than the target value for the
discharge pressure or the condensing temperature at the compressor
in a case where all of the operating indoor units are performing
the heating operation.
10. The air-conditioning apparatus of claim 9, wherein the target
value for the discharge pressure or the condensing temperature in
the heating main operation is determined based on the target value
for the discharge pressure or the condensing temperature when all
of the operating indoor units are performing the heating operation,
capacities of the intermediate heat exchangers, and heat exchange
capacities of the indoor units performing the heating
operation.
11. The air-conditioning apparatus of claim 9, wherein the target
value for a suction pressure, the discharge pressure, an
evaporating temperature, or the condensing temperature in the
heating main operation is set based on an output value of a pump
that drives the secondary-side heat transfer medium in the
secondary-side cycle.
12. The air-conditioning apparatus of claim 9, wherein a difference
in a load capacity between cooling and heating modes of the indoor
units is different from a difference in a heat exchange capacity
between cooling and heating modes of the intermediate heat
exchangers.
13. The air-conditioning apparatus of claim 9, wherein the number
of the indoor units connected to the relay unit is greater than the
number of the intermediate heat exchangers.
14. The air-conditioning apparatus of claim 9, wherein a control
target value for the secondary-side cycle is set in accordance with
heat exchange capacities and operation modes of the indoor units,
and a control target value for the primary-side cycle is set to be
equivalent to the control target value for the secondary-side
cycle.
15. The air-conditioning apparatus of claim 9, wherein both in a
case where at least one of the intermediate heat exchangers
operates as an evaporator and in a case where at least one of the
intermediate heat exchangers operates as a condenser, a flow of the
secondary-side heat transfer medium is operable so that a flow of
the primary-side heat transfer medium and the flow of the
secondary-side heat transfer medium are opposed to each other.
16. The air-conditioning apparatus of claim 9, wherein the
intermediate heat exchangers have different heat transfer areas,
and the intermediate heat exchangers serve as evaporators or
condensers in accordance with a heat exchange capacity and an
operation mode.
Description
TECHNICAL FIELD
The present invention relates to an air-conditioning apparatus
using a refrigeration cycle and, more particularly, to an
air-conditioning apparatus that performs heat transport of cooling
energy or heating energy generated in a refrigeration cycle to a
use-side heat exchanger using a different heat medium.
BACKGROUND ART
A cooling and heating simultaneous air-conditioning apparatus in
which a relay unit and a plurality of indoor units are connected to
an outdoor unit and which is capable of performing a cooling
operation in which the operation mode of an operating indoor unit
is cooling only, a heating operation in which the operation mode of
an operating indoor unit is heating only, and a mixed
(simultaneous) operation in which indoor units perform cooling and
heating, is available (see, for example, Patent Literatures 1 to
3).
Patent Literature 1 describes a method for controlling the
compressor frequency of the cooling and heating simultaneous
air-conditioning apparatus and the heat exchange capacity of an
outdoor heat exchanger.
Furthermore, Patent Literatures 2 and 3 describe a system in which
an intermediate heat exchanger is provided in a relay unit and
which performs a cooling and heating simultaneous operation in
which heat transport from an outdoor unit to the relay unit is
performed using a refrigerant, heat exchange between the
refrigerant and brine in a refrigeration cycle is performed in the
intermediate heat exchanger, and heat transport from the relay unit
to an indoor unit is performed using the brine, and a control
method on the water side.
CITATION LIST
Patent Literatures
Patent Literature 1: Japanese Unexamined Patent Application
Publication No. 4-6374 (FIG. 1)
Patent Literature 2: PCT International Publication No. WO10/131378
(FIG. 12)
Patent Literature 3: PCT International Publication No. WO10-050000
(FIG. 3)
SUMMARY OF INVENTION
Technical Problem
In the cooling and heating simultaneous air-conditioning apparatus
described in Patent Literature 1, a method for controlling the
condensing temperature and the evaporating temperature of the
refrigerant in the compressor and the indoor unit at predetermined
target values in order to exhibit a capacity corresponding to the
load of the indoor unit is described.
In contrast, in the air-conditioning apparatus described in Patent
Literatures 2 and 3, typically, the number of installed
intermediate heat exchangers is smaller than the number of
connected indoor units. Thus, the heat exchange capacity of the
intermediate heat exchangers cannot be changed continuously upon ON
or OFF of cooling and heating of the indoor units. This poses a
problem that even when the condensing temperature and the
evaporating temperature are controlled at predetermined values, the
cooling and heating capacities may vary depending on the load and
the operation modes of the indoor units.
The present invention has been made to solve the above-mentioned
problem, and has as its object to provide an air-conditioning
apparatus which maintains cooling and heating capacities even when
the load conditions vary and which is capable of operating in a
state where the cycle efficiency is high.
Solution to Problem
An air-conditioning apparatus according to the present invention
includes a heat source unit including a compressor, a first flow
passage switching valve that switches a flow passage of a first
refrigerant, and a heat-source-side heat exchanger; a plurality of
indoor units each including a use-side heat exchanger; and a relay
unit including a plurality of intermediate heat exchangers, second
flow passage switching valves that switch operation of the indoor
units between heating and cooling, and third flow passage switching
valves that switch connection of the intermediate heat exchangers
between a condenser and an evaporator. In the air-conditioning
apparatus, a primary-side cycle is formed through which a
primary-side heat transfer medium circulates between the heat
source unit and the relay unit, a secondary-side cycle is formed
through which a secondary-side heat transfer medium circulates
between the relay unit and the indoor units, and heat exchange is
performed between the primary-side cycle and the secondary-side
cycle in the intermediate heat exchangers. When all of operating
indoor units out of the plurality of indoor units are performing a
cooling operation, the third flow passage switching valves are
controlled such that the number of the intermediate heat exchangers
operating as evaporators is greater than in a cooling main
operation in which the indoor unit performing cooling and the
indoor unit performing heating exist at the same time and the first
flow passage switching valve is controlled so that the
heat-source-side heat exchanger operates by being connected to a
discharge side of the compressor. During the cooling main
operation, a target value for a suction pressure or an evaporating
temperature at the compressor is set equal to or lower than a case
where all of the operating indoor units are performing the cooling
operation, and a frequency of the compressor and a capacity of the
heat-source-side heat exchanger are controlled.
An air-conditioning apparatus according to the present invention
includes a heat source unit including a compressor, a first flow
passage switching valve that switches a flow passage of a first
refrigerant, and a heat-source-side heat exchanger; a plurality of
indoor units each including a use-side heat exchanger; and a relay
unit including a plurality of intermediate heat exchangers, second
flow passage switching valves that switch operation of the indoor
units between heating and cooling, and third flow passage switching
valves that switch connection of the intermediate heat exchangers
between a condenser and an evaporator. In the air-conditioning
apparatus, a primary-side cycle is formed through which a
primary-side heat transfer medium circulates between the heat
source unit and the relay unit, a secondary-side cycle is formed
through which a secondary-side heat transfer medium circulates
between the relay unit and the indoor units, and heat exchange is
performed between the primary-side cycle and the secondary-side
cycle in the intermediate heat exchangers. When all of operating
indoor units out of the plurality of indoor units are performing a
heating operation, the third flow passage switching valves are
controlled such that the number of the intermediate heat exchangers
operating as condensers is greater than in a heating main operation
in which the indoor unit performing cooling and the indoor unit
performing heating exist at the same time and the first flow
passage switching valve is controlled so that the heat-source-side
heat exchanger operates by being connected to a suction side of the
compressor. During the heating main operation, a target value for a
discharge pressure or a condensing temperature at the compressor is
set equal to or higher than a case where all of the operating
indoor units are performing the heating operation, and a frequency
of the compressor and a capacity of the heat-source-side heat
exchanger are controlled.
Advantageous Effects of Invention
In an air-conditioning apparatus according to the present
invention, even when the load conditions vary, cooling and heating
capacities are maintained, and operation can be performed in a
state where the cycle efficiency, such as COP, is high.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a refrigerant circuit diagram illustrating an example of
the refrigerant circuit configuration of an air-conditioning
apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a refrigerant circuit diagram illustrating another
example of the refrigerant circuit configuration of the
air-conditioning apparatus according to Embodiment 1 of the present
invention.
FIG. 3 is a P-h diagram illustrating the transition of refrigerant
in a cooling operation.
FIG. 4 is a P-h graph illustrating the transition of refrigerant in
a heating operation.
FIG. 5 is a P-h graph illustrating the transition of refrigerant in
a cooling main operation.
FIG. 6 is a P-h diagram illustrating the transition of refrigerant
in a heating main operation.
FIG. 7 is a P-h diagram illustrating another example of the
transition of refrigerant in the heating main operation.
FIG. 8 is a flowchart illustrating the flow of a control process at
the time of a cooling main operation of the air-conditioning
apparatus according to Embodiment 1 of the present invention.
FIG. 9 is a flowchart illustrating the flow of a control process at
the time of a heating main operation of the air-conditioning
apparatus according to Embodiment 1 of the present invention.
FIG. 10 is a schematic circuit configuration diagram illustrating
an example of a refrigerant circuit configuration of an
air-conditioning apparatus according to Embodiment 2 of the present
invention.
FIG. 11 is a schematic circuit configuration diagram illustrating
an example of a refrigeration cycle configuration of an
air-conditioning apparatus according to Embodiment 3 of the present
invention.
DESCRIPTION OF EMBODIMENTS
Embodiments of the present invention will be described hereinafter
with reference to the accompanying drawings.
Embodiment 1
FIG. 1 is a refrigerant circuit diagram illustrating an example of
the refrigerant circuit configuration of an air-conditioning
apparatus 100 according to Embodiment 1 of the present invention.
FIG. 2 is a refrigerant circuit diagram illustrating another
example of the refrigerant circuit configuration of the
air-conditioning apparatus 100 according to Embodiment 1 of the
present invention. The circuit configuration and operation of the
air-conditioning apparatus 100 will be explained with reference to
FIGS. 1 and 2. The air-conditioning apparatus allows each indoor
unit to freely select a cooling mode or a heating mode using a
refrigeration cycle. In the drawings provided below including FIG.
1, the size relationship of individual components may be different
from the actual size relationship.
In FIG. 1, the air-conditioning apparatus 100 includes a heat
source unit (outdoor unit) A, a plurality of indoor units C to E
connected in parallel, and a relay unit B interposed between the
heat source unit A and the indoor units C to E. In Embodiment 1,
the case where one relay unit and three indoor units are connected
to one heat source unit will be explained. However, the
illustration is not intended to limit the number of the units
connected. For example, two or more heat source units, two or more
relay units, and two or more indoor units may be connected.
Furthermore, the number of operating indoor units connected to the
relay unit B may be larger than the number of intermediate heat
exchangers within the relay unit B, which will be described later,
and even when the number of installed intermediate heat exchangers
is equal to the number of connected indoor units, the variation
range of the capacity of the intermediate heat exchangers may be
different from the variation range of the capacity of the indoor
units. This represents, for example, the case in which two
intermediate heat exchangers are mounted in the relay unit B, two
indoor units are connected to the relay unit B, the heat exchange
capacities of the two intermediate heat exchangers are the same,
and the capacities of the two indoor units are different. However,
Embodiment 1 assumes that the capacities of the indoor units C to E
are the same and the capacities of the two intermediate heat
exchangers are the same.
A primary-side cycle through which a primary-side heat transfer
medium (referred to as refrigerant, hereinafter) circulates is
formed between the heat source unit A and the relay unit B, a
secondary-side cycle through which a secondary-side heat transfer
medium (referred to as brine, hereinafter) circulates is formed
between the relay unit B and each of the indoor units C to E, and
heat exchange between the primary-side cycle and the secondary-side
cycle is performed in intermediate heat exchangers 9a and 9b
arranged within the relay unit B. That is, in the air-conditioning
apparatus 100, cooling energy and heating energy generated by the
heat source unit A are transferred to the indoor units C to E via
the intermediate heat exchangers 9a and 9b of the relay unit B.
As the refrigerant, a refrigerant used in a vapor-compression heat
pump, such as a fluorocarbon refrigerant (for example, an HFC-type
refrigerant, such as an R32 refrigerant, R125, or R134a, a mixture
of the above refrigerants, such as R410A, R407c, R404A, or the
like), an HFO refrigerant (for example, HFO-1234yf, HFO-1234ze(E),
or HFO-1234ze(Z)), a CO.sub.2 refrigerant, an HC refrigerant (for
example, propane or isobutane refrigerant), an ammonia refrigerant,
or a mixed refrigerant of the above refrigerants, such as a mixed
refrigerant of R32 and HFO-1234yf, may be used. Furthermore, as the
brine, water, antifreeze, or water containing an anti-corrosion
material as an additive may be used.
[Heat Source Unit A]
The heat source unit A is typically positioned in a space outside a
construction, such as a building (for example, a rooftop or the
like), and supplies cooling energy or heating energy to the indoor
units C to E via the relay unit B. However, the heat source unit A
need not be installed outdoors. For example, the heat source unit A
may be installed in an enclosed space, such as a machine room
equipped with an ventilation opening. The heat source unit A may be
installed inside a construction as long as waste heat can be
exhausted outside the construction via an exhaust duct.
Alternatively, a heat source unit A of a water-cooled type may be
installed inside a construction. The area in which the heat source
unit A is installed is irrelevant to any particular problem
involved.
The heat source unit A includes a compressor 1, a four-way valve 2,
which serves as a first flow passage switching valve that switches
the direction in which a refrigerant circulates, a heat-source-side
heat exchanger 3, and an accumulator 4. The above-mentioned
components are connected by a first refrigerant pipe 6 and a second
refrigerant pipe 7. In the vicinity of the heat-source-side heat
exchanger 3, a flow control device 3-m for controlling the flow
rate of fluid that exchanges heat with a refrigerant is installed.
Hereinafter, a heat-source-side heat exchanger 3 of an air-cooled
type will be explained as an example of the heat-source-side heat
exchanger 3 and a fan 3-m will be explained as an example of the
flow control device 3-m. However, a heat-source-side heat exchanger
3 of another type, such as a water-cooled type (in this case, the
flow control device 3-m is a pump), may be used as long as a
refrigerant exchanges heat with another fluid. A method for
controlling the compressor 1 and the fan 3-m, and a method for
switching the four-way valve 2 will be described later.
The heat source unit A also includes a first connecting pipe 60A, a
second connecting pipe 60B, a check valve 14, a check valve 16, a
check valve 17, and a check valve 15. By providing the first
connecting pipe 60A, the second connecting pipe 60B, the check
valve 14, the check valve 16, the check valve 17, and the check
valve 15, a high-pressure refrigerant flows out of the heat source
unit A via the first refrigerant pipe 6 and a low-pressure
refrigerant flows into the heat source unit A via the second
refrigerant pipe 7, regardless of the direction in which the
four-way valve 2 is connected.
The compressor 1 sucks a heat-source-side refrigerant and
compresses the heat-source-side refrigerant into a high-temperature
and high-pressure state, and is desirably configured as, for
example, a capacity-controllable inverter compressor or the like.
The four-way valve 2 switches between the flow of the
heat-source-side refrigerant at the time of a heating operation (in
a heating only operation mode and a heating main operation mode)
and the flow of the heat-source-side refrigerant at the time of a
cooling operation (in a cooling only operation mode and a cooling
main operation mode). The heat-source-side heat exchanger (outdoor
heat exchanger) 3 functions as an evaporator during a heating
operation while functioning as a condenser (or a radiator) during a
cooling operation, exchanges heat between air supplied from the fan
3-m and the heat-source-side refrigerant, and transforms the
heat-source-side refrigerant into vapor or condensate according to
the circumstances involved. The accumulator 4 is provided on the
suction side of the compressor 1, and stores an excess refrigerant
generated due to the difference between a heating operation and a
cooling operation or an excess refrigerant generated due to a
transient change in operation.
The check valve 14 is provided at the first refrigerant pipe 6
between the heat-source-side heat exchanger 3 and the relay unit B,
and allows the heat-source-side refrigerant to flow only in a
predetermined direction (the direction from the heat source unit A
to the relay unit B). The check valve 15 is provided at the second
refrigerant pipe 7 between the relay unit B and the four-way valve
2, and allows the heat-source-side refrigerant to flow only in
another predetermined direction (the direction from the relay unit
B to the heat source unit A). The check valve 16 is provided at the
first connecting pipe 60a, and causes the heat-source-side
refrigerant discharged from the compressor 1 to circulate to the
relay unit B during a heating operation. The check valve 17 is
provided at the connecting pipe 60b, and causes the
heat-source-side refrigerant returned from the relay unit B to
circulate to the suction side of the compressor 1 during a heating
operation.
The first connecting pipe 60a connects between the second
refrigerant pipe 7 between the four-way valve 2 and the check valve
15, and the first refrigerant pipe 6 between the check valve 14 and
the relay unit B, within the heat source unit A. The second
connecting pipe 60b connects between the second refrigerant pipe 7
between the check valve 15 and the relay unit B, and the first
refrigerant pipe 6 between the heat-source-side heat exchanger 3
and the check valve 14, within the heat source unit A.
The heat source unit A moreover includes a pressure gauge 31, a
pressure gauge 32, and a thermometer 41. The pressure gauge 31 is
provided on the discharge side of the compressor 1 and measures the
pressure of the refrigerant discharged from the compressor 1. The
pressure gauge 32 is provided on the suction side of the compressor
1 and measures the pressure of the refrigerant sucked into the
compressor 1. The thermometer 41 is provided in the vicinity of the
heat-source-side heat exchanger 3 and measures the temperature of
the outside air taken in by the fan 3-m. The pieces of information
(temperature information and pressure information) detected by the
above-mentioned detection devices are sent to a controller (for
example, control means 50) that performs overall control of the
operation of the air-conditioning apparatus 100, and are used to
control each actuator.
[Relay Unit B]
The relay unit B is installed in, for example, a space on, for
example, the lower side of the roof, which is formed inside a
construction but is different from an indoor space, and transfers,
to the indoor units C to E, cooling energy or heating energy
supplied from the heat source unit A. However, the relay unit B may
be installed in a shared space in which an elevator or the like is
installed, or the like.
As branch portions on the refrigerant side, the relay unit B
includes a first branch portion 8a into which a high-pressure
refrigerant flows from the heat source unit A, a second branch
portion 8b from which a low-pressure refrigerant flows out towards
the heat source unit A, and a third branch portion 8c in which the
refrigerant has an intermediate pressure. Furthermore, as branch
portions on the brine side, the relay unit B includes a fourth
branch portion 8d and a fifth branch portion 8e corresponding to
the high-pressure side of brine, and a sixth branch portion 8f and
a seventh branch portion 8g corresponding to the low-pressure side
of brine.
Furthermore, the relay unit B includes the first intermediate heat
exchanger 9a and the second intermediate heat exchanger 9b which
exchange heat between a refrigerant and a second refrigerant, a
first pump 18a and a second pump 18b which drive the second
refrigerant, a first flow control device 10a which controls the
flow rate of the refrigerant, a second flow control device 10b
which controls the flow rate of the refrigerant, a third flow
control device 12a which controls the flow rate of the refrigerant,
a fourth flow control device 12b which controls the flow rate of
the refrigerant, and a refrigerant-refrigerant heat exchanger 13
which exchanges heat between refrigerants.
At the first branch portion 8a, the first refrigerant pipe 6 is
branched in order to connect the first refrigerant pipe 6 to each
of the intermediate heat exchangers 9a and 9b. At the second branch
portion 8b, the second refrigerant pipe 7 is branched in order to
connect the second refrigerant pipe 7 to each of the intermediate
heat exchangers 9a and 9b. The third branch portion 8c is provided
between the first flow control device 10a and the second flow
control device 10b, and the third flow control device 12a and the
fourth flow control device 12b, and connects the intermediate heat
exchangers 9a and 9b in series or in parallel.
A first solenoid valve 11a is provided at the pipe between the
first branch portion 8a and the intermediate heat exchanger 9a. A
second solenoid valve 11b is provided at the pipe between the first
branch portion 8a and the intermediate heat exchanger 9b. A third
solenoid valve 11c is provided at the pipe between the second
branch portion 8b and the intermediate heat exchanger 9a. A fourth
solenoid valve 11d is provided at the pipe between the second
branch portion 8b and the intermediate heat exchanger 9b. The first
solenoid valve 11a, the second solenoid valve 11b, the third
solenoid valve 11c, and the fourth solenoid valve 11d each operate
as a third flow passage switching valve for selectively switching
the connection of the intermediate heat exchanger 9a or 9b between
a condenser and an evaporator, and each allow the intermediate heat
exchanger 9a or 9b to be switchably connected to the first branch
portion 8a or the second branch portion 8b.
The first solenoid valve 11a and the third solenoid valve 11c are
installed on a side opposite to the side of the first flow control
device 10a with respect to the intermediate heat exchanger 9a.
Furthermore, the second solenoid valve 11b and the fourth solenoid
valve 11d are installed on a side opposite to the side of the
second flow control device 10b with respect to the intermediate
heat exchanger 9b. The flow of refrigerant in the intermediate heat
exchangers 9a and 9b will be explained later in [Circuit
Configuration].
The fourth branch portion 8d branches the brine that has flowed out
of the intermediate heat exchanger 9a into the first brine pipes
6c, 6d, and 6e. The fifth branch portion 8e branches the brine that
has flowed out of the intermediate heat exchanger 9b into the first
brine pipes 6c, 6d and 6e. The sixth branch portion 8f combines the
brines that have flowed through the second brine pipes 7c, 7d and
7e together, and allows the combined brine to flow into the
intermediate heat exchanger 9a. The seventh branch portion 8g
combines the brines that have flowed through the second brine pipes
7c, 7d and 7e together, and allows the combined brine to flow into
the intermediate heat exchanger 9b.
A switching valve 19c is installed at the first brine pipe 6c
between the fourth branch portion 8d and an indoor heat exchanger
(use-side heat exchanger) 5c. A switching valve 19d is installed at
the first brine pipe 6d between the fourth branch portion 8d and an
indoor heat exchanger 5d. A switching valve 19e is installed at the
first brine pipe 6e between the fourth branch portion 8d and an
indoor heat exchanger 5e. A switching valve 19f is installed at the
first brine pipe 6c between the fifth branch portion 8e and the
indoor heat exchanger 5c. A switching valve 19g is installed at the
first brine pipe 6d between the fifth branch portion 8e and the
indoor heat exchanger 5d. A switching valve 19h is installed at the
first brine pipe 6e between the fifth branch portion 8e and the
indoor heat exchanger 5e.
The switching valves 19c, 19d, 19e, 19f, 19g, and 19h operate as
second flow passage switching valves that switch the flow passage
of brine, and allow the indoor units C to E to be switchably
connected to the fourth branch portion 8d or the fifth branch
portion 8e.
A switching valve 19i is installed at the second brine pipe 7c
between the sixth branch portion 8f and the indoor heat exchanger
5c. A switching valve 19j is installed at the second brine pipe 7d
between the sixth branch portion 8f and the indoor heat exchanger
5d. A switching valve 19k is installed at the second brine pipe 7e
between the sixth branch portion 8f and the indoor heat exchanger
5e. A switching valve 19l is installed at the second brine pipe 7c
between the seventh branch portion 8g and the indoor heat exchanger
5c. A switching valve 19m is installed at the second brine pipe 7d
between the seventh branch portion 8g and the indoor heat exchanger
5d. A switching valve 19n is installed at the second brine pipe 7e
between the seventh branch portion 8g and the indoor heat exchanger
5e.
The switching valves 19i, 19j, 19k, 19l, 19m, and 19n operate as
second flow passage switching valves which switch the flow passage
of brine, and allow the indoor units C to E to be switchably
connected to the sixth branch portion 8f or the seventh branch
portion 8g.
In Embodiment 1, the case in which two sets of intermediate heat
exchangers, flow control devices, and pumps are installed will be
exemplified. However, the number of the components installed is not
limited to that as illustrated. That is, the air-conditioning
apparatus 100 includes a plurality of intermediate heat exchangers
installed to be capable of a cooling and heating simultaneous
operation. As the number of sets of intermediate heat exchangers,
flow control devices, and pumps increases, the heat exchange
capacities for cooling and heating of the intermediate heat
exchangers can be stably, continuously switched according to the
load of an indoor unit.
The relay unit B includes thermometers 33a to 33d that measure the
temperatures of refrigerant at the inlets and outlets of the
intermediate heat exchangers 9a and 9b, a thermometer 33e that
measures the temperature of refrigerant between the
refrigerant-refrigerant heat exchanger 13 and the second branch
portion 8b, thermometers 34a and 34b that measure the temperatures
of brine on the downstream sides of the first pump 18a and the
second pump 18b, respectively, and thermometers 34c to 34e that
measure the temperatures of brine between the indoor heat
exchangers 5c to 5e and flow control devices 20c to 20e,
respectively. The pieces of information (temperature information)
detected by the above-mentioned detection devices are sent to a
controller (for example, control means 51) that performs overall
control of the operation of the air-conditioning apparatus 100, and
are used to control each actuator.
[Indoor Units C to E]
The indoor units C to E are each installed at a position from which
conditioned air can be supplied to an air-conditioning target
space, such as an indoor space, and each supply cooling air or
heating air to the air-conditioning target space using cooling
energy or heating energy from the heat source unit A transferred
via the relay unit B.
The indoor heat exchanger 5 is mounted in each of the indoor units
C to E. Reference symbols c to e are assigned to the indoor heat
exchangers 5 in correspondence with the indoor units C to E,
respectively. The indoor heat exchanger 5c is connected to the
sixth branch portion 8f or the seventh branch portion 8g of the
relay unit B via the second brine pipe 7c, and is connected to the
fourth branch portion 8d or the fifth branch portion 8e of the
relay unit B via the first brine pipe 6c. The indoor heat exchanger
5d is connected to the sixth branch portion 8f or the seventh
branch portion 8g of the relay unit B via the second brine pipe 7d,
and is connected to the fourth branch portion 8d or the fifth
branch portion 8e of the relay unit B via the first brine pipe 6d.
The indoor heat exchanger 5e is connected to the sixth branch
portion 8f or the seventh branch portion 8g of the relay unit B via
the second brine pipe 7e, and is connected to the fourth branch
portion 8d or the fifth branch portion 8e of the relay unit B via
the first brine pipe 6e.
The indoor heat exchangers 5 each exchange heat between air
supplied from an air-sending device of a fan 5-m and a heat medium,
and generate heating air or cooling air to be supplied to the
air-conditioning target space. Furthermore, in the vicinity of each
of the indoor heat exchangers 5, a flow control device 5-m that
controls the flow rate of fluid that exchanges heat with
refrigerant is installed. Hereinafter, indoor heat exchangers 5 of
an air-cooled type will be taken as an example of the indoor heat
exchangers 5, and fans 5-m will be taken as an example of the flow
control devices 5-m. However, indoor heat exchangers 5 of a
different type, such as a water-cooled type (in this case, the flow
control devices 5-m are pumps), may be used as long as refrigerant
exchanges heat with another fluid. Reference symbols c to e are
assigned to the fans 5-m in correspondence with the indoor units C
to E, respectively.
Thermometers 42-c to 42-e that measure the current temperatures of
air-conditioning target spaces, such as indoor spaces, are provided
in the indoor units C to E, respectively. The pieces of information
(temperature information) detected by these detection devices are
sent to controllers (for example, control means 52c, 52d, and 52e)
that perform overall control of the operation of the
air-conditioning apparatus 100, and are used to control each
actuator.
[Pipes]
A narrow pipe that connects between the heat-source-side heat
exchanger 3 and the first branch portion 8a of the relay unit B is
referred to as the first refrigerant pipe 6. Pipes that connect
between the indoor heat exchangers 5c, 5d, and 5e of the indoor
units C, D, and E and the fourth branch portion 8d or the fifth
branch portion 8e of the relay unit B are referred to as the first
brine pipes 6c, 6d, and 6e. The first brine pipes 6c, 6d, and 6e
correspond to the first refrigerant pipe 6.
A pipe that has a width larger than that of the first refrigerant
pipe 6 and connects between the four-way valve 2 and the second
branch portion 8b of the relay unit B is referred to as the second
refrigerant pipe 7. Pipes that connect between the indoor heat
exchangers 5c, 5d, and 5e of the indoor units C, D, and E and the
sixth branch portion 8f or the seventh branch portion 8g of the
relay unit B are referred to as the second brine pipes 7c, 7d, and
7e. The second brine pipes 7c, 7d, and 7e correspond to the second
refrigerant pipe 7.
Accordingly, the refrigerant flows from the heat source unit A to
the relay unit B in the first refrigerant pipe 6 and flows from the
relay unit B to the heat source unit A in the second refrigerant
pipe 7. Furthermore, brine, serving as the second refrigerant,
flows from the relay unit B to the indoor units C to E in the first
brine pipes 6c to 6e, respectively, and flows from the indoor units
C to E to the relay unit B in the second brine pipes 7c to 7e,
respectively.
[Circuit Configuration]
The circuit configuration of the primary-side cycle in the heat
source unit A and the relay unit B will be explained first. The
primary-side cycle refers to a cycle through which a refrigerant
circulates. In the heat source unit A, the four-way valve 2 is
selectively switched in accordance with the operation of the
heat-source-side heat exchanger 3. That is, the four-way valve 2 is
switched to the direction represented by the solid lines in the
drawing in the case where the heat-source-side heat exchanger 3
operates as a condenser that transfers heat from the refrigerant to
air, and is switched to the direction represented by the broken
lines in the drawing in the case where the heat-source-side heat
exchanger 3 operates as an evaporator that receives heat from
air.
In the case where a CO.sub.2 refrigerant is used as the
refrigerant, since the critical temperature is as low as about 30
degrees Centigrade, and a supercritical range is reached in the
course of heat transfer, the heat-source-side heat exchanger 3 can
rather be said to act as a radiator. However, in the present
specification, the heat-source-side heat exchanger 3 is described
as a condenser, in correspondence with an evaporator.
In the relay unit B, when all operating indoor units out of the
indoor units C to E are performing cooling, both the intermediate
heat exchangers 9a and 9b operate as evaporators. When all
operating indoor units out of the indoor units C to E are
performing heating, both the intermediate heat exchangers 9a and 9b
operate as condensers. When operating indoor units out of the
indoor units C to E are performing cooling and heating in
combination, one of the intermediate heat exchangers 9a and 9b
operates as a condenser and the other one of the intermediate heat
exchangers 9a and 9b operates as an evaporator. In a cooling
operation and a heating operation, the capacities of the
intermediate heat exchangers are increased using both the
intermediate heat exchangers 9a and 9b as evaporators or
condensers, thereby improving their cooling and heating
performance.
Here, in the case where the first solenoid valve 11a and the second
solenoid valve 11b are opened and the third solenoid valve 11c and
the fourth solenoid valve 11d are closed, the intermediate heat
exchangers 9a and 9b operate as condensers. Also, in the case where
the third solenoid valve 11c and the fourth solenoid valve 11d are
opened and the first solenoid valve 11a and the second solenoid
valve 11b are closed, the intermediate heat exchangers 9a and 9b
operate as evaporators. Since the first solenoid valve 11a and the
third solenoid valve 11c are not opened at the same time and the
second solenoid valve 11b and the fourth solenoid valve 11d are not
opened at the same time, they may be replaced with three-way valves
or the like.
The first flow control device 10a and the second flow control
device 10b connect the intermediate heat exchangers 9a and 9b to
the third branch portion 8c. With reference to the pieces of
temperature information obtained by the thermometers 33a to 33d,
the first flow control device 10a and the second flow control
device 10b are adjusted on the basis of the degree of superheat of
refrigerant at the outlet of an intermediate heat exchanger when
the intermediate heat exchanger operates as an evaporator, and are
adjusted on the basis of the degree of subcooling of refrigerant at
the outlet of an intermediate heat exchanger when the intermediate
heat exchanger operates as a condenser. The evaporating temperature
and the condensing temperature necessary to calculate the degree of
superheat and the degree of subcooling of refrigerant at the outlet
of an intermediate heat exchanger may be calculated from the pieces
of information obtained using the pressure gauges 31 and 32
installed within the heat source unit A, which will be described
below, or may be calculated by installing pressure gauges at the
first branch portion 8a and the second branch portion 8b within the
relay unit B and referring to the values detected by the pressure
gauges.
In the following description, assume that in a cooling operation in
which all operating indoor units are performing cooling, the third
solenoid valve 11c and the fourth solenoid valve 11d are opened,
the first solenoid valve 11a and the second solenoid valve 11b are
closed, and both the intermediate heat exchangers 9a and 9b operate
as evaporators. Assume also that in a heating operation in which
all operating indoor units are performing heating, the first
solenoid valve 11a and the second solenoid valve 11b are opened,
the third solenoid valve 11c and the fourth solenoid valve 11d are
closed, and both the intermediate heat exchangers 9a and 9b operate
as condensers. Assume moreover that in a cooling and heating
simultaneous operation in which an indoor unit performing cooling
and an indoor unit performing heating exist at the same time, the
first solenoid valve 11a and the fourth solenoid valve 11d are
opened, the second solenoid valve 11b and the third solenoid valve
11c are opened, the intermediate heat exchanger 9a operates as a
condenser, and the intermediate heat exchanger 9b operates as an
evaporator.
The third flow control device 12a connects between the first branch
portion 8a and the third branch portion 8c, and adjusts the flow
rate of refrigerant bypassing the intermediate heat exchangers 9a
and 9b. The fourth flow control device 12b connects between the
third branch portion 8c and the second branch portion 8b, and
adjusts the flow rate of refrigerant bypassing the intermediate
heat exchangers 9a and 9b.
The refrigerant-refrigerant heat exchanger 13 exchanges heat
between the refrigerant flowing through the passage between the
first flow control device 12a and the third branch portion 8c and
the refrigerant flowing through the passage between the fourth flow
control device 12b and the second branch portion 8b. The
refrigerant-refrigerant heat exchanger 13 cools the refrigerant
flowing into the first flow control device 10a, the second flow
control device 10b, and the fourth flow control device 12b in the
case where the intermediate heat exchanger 9a or 9b operates as an
evaporator. The refrigerant-refrigerant heat exchanger 13 is
installed because the refrigerant flowing into a flow control
device changes from a two-phase gas-liquid state into a
single-liquid-phase state by cooling the refrigerant, thus
achieving stable flow control.
As the operation of the third flow control device 12a and the
fourth flow control device 12b in each operation mode, during, for
example, a cooling operation, the third flow control device 12a is
fully opened, and the opening degree of the fourth flow control
device 12b is controlled on the basis of the degree of superheat of
the low-pressure-side refrigerant at the outlet of the
refrigerant-refrigerant heat exchanger 13 by referring to the
thermometer 33e. Furthermore, during a cooling and heating
simultaneous operation, both the third flow control device 12a and
the fourth flow control device 12b are fully closed. Moreover,
during a heating operation, the third flow control device 12a is
fully closed, and the fourth flow control device 12b is fully
opened.
Basically, the third flow control device 12a does not adjust the
flow rate of the refrigerant bypassing a condenser. Therefore, the
third flow control device 12a may be an opening and closing valve,
such as a solenoid valve, as illustrated in FIG. 1. Furthermore,
the refrigerant-refrigerant heat exchanger 13 may be omitted, and a
refrigerant circuit may be arranged in such a manner that the
refrigerant flowing out of the intermediate heat exchanger 9a
serving as a condenser passes through the refrigerant-refrigerant
heat exchanger 13 into the third branch portion 8c during a cooling
and heating simultaneous operation.
The circuit configuration of the secondary-side cycle in the relay
unit B will be explained next. The secondary-side cycle is a cycle
through which the second refrigerant circulates. The intermediate
heat exchangers 9a and 9b are connected by pipes in such a manner
that the flow of the refrigerant in the primary-side cycle and the
flow of brine in the secondary-side cycle are opposed to each other
in the case where the intermediate heat exchangers 9a and 9b
operate as condensers. With this configuration, when the
intermediate heat exchangers 9a and 9b operate as evaporators, only
the flow direction of refrigerant changes, and operation is
performed in which the flow of the refrigerant and the flow of
brine are in parallel to each other. However, by installing valves
at an inlet and an outlet of brine of an intermediate heat
exchanger so that the flow of brine flowing into or out of the
intermediate heat exchangers 9a and 9b can be changed, to perform
control to achieve opposed flows both for a condenser and an
evaporator, efficient heat exchange can be achieved.
As illustrated in FIG. 2, flow passage switching valves 21a and 21b
that change the flow of brine in an intermediate heat exchanger may
not be attached at the intermediate heat exchanger 9a but may be
attached only at the intermediate heat exchanger 9b operating as an
evaporator during a cooling and heating simultaneous operation.
With this arrangement, in a mode in which the intermediate heat
exchanger 9b operates as an evaporator, the flow of the refrigerant
and the flow of brine are opposed to each other in portions other
than the intermediate heat exchanger 9a during a cooling operation.
Therefore, the cooling capacity can be efficiently improved while
suppressing an increase in cost.
Furthermore, the first pump 18a and the second pump 18b of an
inverter type are connected in proximity to the intermediate heat
exchangers 9a and 9b and are connected to the fourth branch portion
8d and the fifth branch portion 8e, respectively. Furthermore, the
other pipes for the intermediate heat exchangers 9a and 9b are
connected to the sixth branch portion 8f and the seventh branch
portion 8g, respectively. The position of the first pump 18a and
the position of the intermediate heat exchanger 9a in the
secondary-side cycle may be inverted. Similarly, the position of
the second pump 18b and the position of the intermediate heat
exchanger 9b in the secondary-side cycle may be inverted.
Since both the intermediate heat exchangers 9a and 9b operate as
evaporators in the case where all operating indoor units are
performing cooling and both the intermediate heat exchangers 9a and
9b operate as condensers in the case where all operating indoor
units are performing heating, the switching valves 19c to 19n may
be connected to either intermediate heat exchanger or all of them
may be opened so that brine flows into the switching valves from
both intermediate heat exchangers. In contrast, during a cooling
and heating simultaneous operation, the switching valves 19c to 19n
are operated in such a manner that an indoor unit performing
cooling is connected to the intermediate heat exchanger 9b
operating as an evaporator and an indoor unit performing heating is
connected to the intermediate heat exchanger 9a operating as a
condenser.
Furthermore, the flow control devices 20c to 20e that adjust the
flow rates of brine flowing into corresponding indoor units are
installed at the second brine pipes 7c to 7e between the indoor
heat exchangers 5c to 5e and the switching valves switching valves
19i to 19n. The flow control devices 20c to 20e may be installed on
the side of the first brine pipes 6c to 6e. The opening degrees of
the flow control devices 20c to 20e are controlled such that, for
example, the differences in temperature of brine at inlets and
outlets of the indoor units C to E stay constant.
As a method for measuring the temperature of brine, measurement of
the inlet and output temperatures of the indoor units C to E is
possible. For example, by defining the temperatures of brine
flowing out of the intermediate heat exchangers 9a and 9b as the
inlet temperatures of the indoor units C to E and defining the
temperature of brine returning from the indoor units C to E to the
relay unit B as the outlet temperatures of the indoor units C to E,
as illustrated in the drawing, control may be performed such that
the differences between the temperatures become equal to a
predetermined value. The temperatures of the brine that has flowed
out of the intermediate heat exchangers 9a and 9b can be measured
by the thermometers 34a and 34b arranged on the downstream side of
the first pump 18a and the second pump 18b, respectively.
Furthermore, the temperatures of the brine returning from the
indoor units C to E to the relay unit B can be measured by the
thermometers 34c to 34e provided between the indoor heat exchangers
5c to 5e and the flow control devices 20c to 20e.
The target value for the temperature difference is set to about 3
to 7 degrees Centigrade for a cooling operation, as described in
Patent Literature 2. By setting the control target value larger in
a heating operation than in cooling, an efficient operation can be
achieved. Furthermore, the first pump 18a and the second pump 18b
may be driven at a constant speed. However, in the flow control
devices 20c to 20e for brine, temperature difference control of
which is in progress, control can be performed by changing the pump
capacity in such a manner that the opening degree of the flow
control device whose opening degree is largest is set to, for
example, 80% to 95% of the maximum opening degree.
[Operation Mode]
A running operation at the time of various operations executed by
the air-conditioning apparatus 100 will be explained next. The
running operation of the air-conditioning apparatus 100 includes
four modes: a cooling operation mode, a heating operation mode, a
cooling main operation mode, and a heating main operation mode.
Hereinafter, the flow of refrigerant and brine in each operation
mode will be explained with reference to P-h diagrams.
A cooling operation is an operation mode in which an indoor unit is
capable of only cooling and the indoor unit is performing cooling
or is stopped. An operation is an operation mode in which an indoor
unit is capable of only heating and the indoor unit is performing
heating or is stopped. A cooling main operation is an operation
mode in which each indoor unit is capable of selecting cooling or
heating and in a cooling and heating simultaneous operation mode in
which an indoor unit performing cooling and an indoor unit
performing heating exist at the same time, the cooling load is
heavier than heating load, and the heat-source-side heat exchanger
3 is connected to the discharge side of the compressor and operates
as a condenser. A heating main operation is an operation mode in
which in a cooling and heating simultaneous operation, the heating
load is heavier than the cooling load, and the heat-source-side
heat exchanger 3 is connected to the suction side of the compressor
and operates as an evaporator.
[Cooling Operation]
The case where all the indoor units C, D, and E intend to perform
cooling will be explained hereinafter. In cooling, the four-way
valve 2 is switched so that the refrigerant discharged from the
compressor 1 flows into the heat-source-side heat exchanger 3. The
third solenoid valve 11c and the fourth solenoid valve 11d are
opened, and the first solenoid valve 11a and the second solenoid
valve 11b are closed. At this time, both the first intermediate
heat exchanger 9a and the second intermediate heat exchanger 9b
operate as evaporators. FIG. 3 is a P-h diagram illustrating the
transition of refrigerant in a cooling operation. The flow of
refrigerant will be explained first, and the flow of brine will be
explained next.
In this state, the operation of the compressor 1 starts. A
low-temperature and low-pressure gas refrigerant is compressed by
the compressor 1 and is discharged as a high-temperature and
high-pressure gas refrigerant. In the refrigerant compression
process by the compressor 1, compression is performed in such a
manner that the refrigerant is heated more than when the
refrigerant is adiabatically compressed based on an isentropic line
by an amount corresponding to the adiabatic efficiency of the
compressor, and is represented by a line extending from point (a)
to point (b) in FIG. 3.
The high-temperature and high-pressure gas refrigerant discharged
from the compressor 1 flows into the heat-source-side heat
exchanger 3 via the four-way valve 2. At this time, the refrigerant
is cooled while heating outdoor air, and turns into an
intermediate-temperature and high-pressure liquid refrigerant. The
change of the refrigerant in the heat-source-side heat exchanger 3
is represented by a slightly-slanted substantially horizontal
straight line extending from point (b) to point (c) in FIG. 3, in
view of pressure loss in the heat-source-side heat exchanger 3.
The intermediate-temperature and high-pressure liquid refrigerant
that has flowed out of the heat-source-side heat exchanger 3 passes
through the first refrigerant pipe 6 and the third flow control
device 12a, exchanges heat in the refrigerant-refrigerant heat
exchanger 13 with the refrigerant that has flowed out of the fourth
flow control device 12b, and is cooled. The cooling process at this
time is represented by a line extending from point (c) to point (d)
in FIG. 3.
The liquid refrigerant cooled at the refrigerant-refrigerant heat
exchanger 13 flows into the first flow control device 10a and the
second flow control device 10b while the refrigerant partially
bypasses the second branch portion 8b through the fourth flow
control device 12b. Then, the high-pressure liquid refrigerant is
expanded and decompressed by the first flow control device 10a and
the second flow control device 10b, and turns into a
low-temperature and low-pressure, two-phase gas-liquid state. A
change of the refrigerant occurs with a constant enthalpy at the
first flow control device 10a and the second flow control device
10b. The change of the refrigerant at this time is represented by a
vertical line extending from point (d) to point (e) in FIG. 3.
The low-temperature and low-pressure refrigerant in the two-phase
gas-liquid state that has flowed out of the first flow control
device 10a and the second flow control device 10b flows into the
first intermediate heat exchanger 9a and the second intermediate
heat exchanger 9b. Then, the refrigerant is heated while cooling
brine, and turns into a low-temperature and low-pressure gas
refrigerant. The change of the refrigerant at the first
intermediate heat exchanger 9a and the second intermediate heat
exchanger 9b is represented by a slightly-slanted substantially
horizontal straight line extending from point (e) to point (a) in
FIG. 3, in view of pressure loss.
The low-temperature and low-pressure gas refrigerants that have
flowed out of the first intermediate heat exchanger 9a and the
second intermediate heat exchanger 9b pass through the third
solenoid valve 11c and the fourth solenoid valve 11d, respectively,
and flow into the second branch portion 8b. The low-temperature and
low-pressure gas refrigerants merge together at the second branch
portion 8b. The merged refrigerant passes through the second
refrigerant pipe 7 and the four-way valve 2, flows into the
compressor 1, and is compressed.
Next, the flow of brine will be explained. Since all the indoor
units C, D, and E are performing cooling, the switching valves 19c
to 19h and 19i to 19n for brine are opened, and brines travel from
the fourth branch portion 8d and the fifth branch portion 8e to the
first brine pipes 6c to 6e on the indoor side and from the second
brine pipes 7c to 7e on the indoor side to the sixth branch portion
8f and the seventh branch portion 8g. The brines cooled by the
refrigerant at the first intermediate heat exchanger 9a and the
second intermediate heat exchanger 9b are subjected to
pressurization and driven by the first pump 18a and the second pump
18b, and flow into the fourth branch portion 8d and the fifth
branch portion 8e.
The brines flowing into the fourth branch portion 8d and the fifth
branch portion 8e are mixed at the switching valves 19c to 19h for
brine, and flow into the indoor units C to E through the first
brine pipes 6c to 6e on the indoor side. The brines cool the indoor
air at the indoor heat exchangers 5c to 5e, and cooling is
performed. At the time of cooling, the brines are heated by the
indoor air, pass through the second brine pipes 7c to 7e on the
indoor side, and return to the relay unit B. The brines flow into
the first intermediate heat exchanger 9a and the second
intermediate heat exchanger 9b while being expanded and
decompressed by the flow control devices 20c to 20e for brine.
[Heating Operation]
The case where all the indoor units C, D, E intend to perform
heating will now be explained. In a heating operation, the four-way
valve 2 is switched so that the refrigerant discharged from the
compressor 1 flows into the first branch portion 8a. The first
solenoid valve 11a and the second solenoid valve 11b are opened,
and the third solenoid valve 11c and the fourth solenoid valve 11d
are closed. At this time, both the first intermediate heat
exchanger 9a and the second intermediate heat exchanger 9b operate
as condensers. FIG. 4 is a P-h diagram illustrating the transition
of refrigerant in the heating operation. The flow of refrigerant
will be explained first, and the flow of brine will be explained
next.
In this state, the operation of the compressor 1 starts. A
low-temperature and low-pressure gas refrigerant is compressed by
the compressor 1 and is discharged as a high-temperature and
high-pressure gas refrigerant. The refrigerant compression process
by the compressor is represented by a line extending from point (a)
to point (b) in FIG. 4.
The high-temperature and high-pressure gas refrigerant discharged
from the compressor 1 flows into the first branch portion 8a
through the four-way valve 2 and the first refrigerant pipe 6. The
high-temperature and high-pressure gas refrigerant that has flowed
into the first branch portion 8a is branched at the first branch
portion 8a, and the branched refrigerants pass through the first
solenoid valve 11a and the second solenoid valve 11b, and flow into
the first intermediate heat exchanger 9a and the second
intermediate heat exchanger 9b. The refrigerants are cooled while
heating brine, and turn into intermediate-temperature and
high-pressure liquid refrigerants. The change of the refrigerants
in the first intermediate heat exchanger 9a and the second
intermediate heat exchanger 9b is represented by a slightly-slanted
substantially horizontal straight line extending from point (b) to
point (c) in FIG. 4.
The intermediate-temperature and high-pressure refrigerants that
have flowed out of the first intermediate heat exchanger 9a and the
second intermediate heat exchanger 9b flow into the first flow
control device 10a and the second flow control device 10b, merge
together at the third branch portion 8c, and the merged refrigerant
flows into the fourth flow control device 12b. At this time, the
high-pressure liquid refrigerants are expanded and decompressed at
the first flow control device 10a, the second flow control device
10b, and the fourth flow control device 12b, and turn into a
low-temperature and low-pressure, two-phase gas-liquid state. The
change of the refrigerants at this time is represented by a
vertical line extending from point (c) to point (d) in FIG. 4.
The low-temperature and low-pressure refrigerant in the two-phase
gas-liquid state that has flowed out of the fourth flow control
device 12b passes through the second refrigerant pipe 7, flows into
the heat-source-side heat exchanger 3, is heated while cooling the
outdoor air, and turns into a low-temperature and low-pressure gas
refrigerant. The change of the refrigerant at the heat-source-side
heat exchanger 3 is represented by a slightly-slanted substantially
horizontal straight line extending from point (d) to point (a) in
FIG. 4. The low-temperature and low-pressure gas refrigerant that
has flowed out of the heat-source-side heat exchanger 3 passes
through the four-way valve 2, flows into the compressor 1, and is
compressed.
Next, the flow of brine will be explained. The flow of brine is
substantially similar to that at the time of a cooling operation.
Since all the indoor units C, D, and E are performing heating, the
switching valves 19c to 19h and 19i to 19n for brine are opened,
and brines travel from the fourth branch portion 8d and the fifth
branch portion 8e to the first brine pipes 6c to 6e on the indoor
side and from the second brine pipes 7c to 7e on the indoor side to
the sixth branch portion 8f and the seventh branch portion 8g. The
brines heated by refrigerants at the first intermediate heat
exchanger 9a and the second intermediate heat exchanger 9b are
subjected to pressurization and driven at the first pump 18a and
the second pump 18b, and flow into the fourth branch portion 8d and
the fifth branch portion 8e.
The brines that have flowed into the fourth branch portion 8d and
the fifth branch portion 8e are mixed by the switching valves 19c
to 19h for brine, and pass through the first brine pipes 6c to 6e
on the indoor side and flow into the indoor units C to E. The
brines heat the indoor air at the indoor heat exchangers 5c to 5e,
and heating is performed. At the time of heating, the brines are
cooled by the indoor air, pass through the second brine pipes 7c to
7e on the indoor side, and return to the relay unit B. The brines
flow into the first and second intermediate heat exchangers 9a and
9b while being expanded and decompressed by the flow control
devices 20c to 20e for brine.
[Cooling Main Operation]
The case where the indoor units C and D are performing cooling and
the indoor unit E is performing heating will now be explained. In
this case, the four-way valve 2 is switched so that the refrigerant
discharged from the compressor 1 flows into the heat-source-side
heat exchanger 3. The first solenoid valve 11a and the fourth
solenoid valve 11d are opened, and the second solenoid valve 11b
and the third solenoid valve 11c are closed. At this time, the
first intermediate heat exchanger 9a operates as a condenser and
the second intermediate heat exchanger 9b operates as an
evaporator. FIG. 5 is a P-h diagram illustrating the transition of
refrigerant in the cooling main operation. The flow of refrigerant
will be explained first, and the flow of brine will be explained
next.
In this state, the operation of the compressor 1 starts. A
low-temperature and low-pressure gas refrigerant is compressed by
the compressor 1, and is discharged as a high-temperature and
high-pressure gas refrigerant. The refrigerant compression process
by the compressor is represented by a line extending from point (a)
to point (b) in FIG. 5.
The high-temperature and high-pressure gas refrigerant discharged
from the compressor 1 flows into the heat-source-side heat
exchanger 3 via the four-way valve 2. At this time, in the
heat-source-side heat exchanger 3, the refrigerant is cooled while
heating the outdoor air with a heat quantity necessary for heating
being left intact, and turns into an intermediate-temperature and
high-pressure, two-phase gas-liquid state. The change of the
refrigerant at the heat-source-side heat exchanger 3 is represented
by a slightly-slanted substantially horizontal straight line
extending from point (b) to point (c) in FIG. 5.
The intermediate-temperature and high-pressure, two-phase
gas-liquid refrigerant that has flowed out of the heat-source-side
heat exchanger 3 passes through the first refrigerant pipe 6, the
first branch portion 8a, and the first solenoid valve 11a, and
flows into the first intermediate heat exchanger 9a. Then, the
refrigerant is cooled while heating brine, and turns into an
intermediate-temperature and high-pressure liquid refrigerant. The
change of the refrigerant at the first intermediate heat exchanger
9a is represented by a slightly-slanted substantially horizontal
straight line extending from point (c) to point (d) in FIG. 5. The
refrigerant that has flowed out of the intermediate heat exchanger
9a is expanded and decompressed by the first flow control device
10a. The change of the refrigerant at this time is represented by a
vertical line extending from point (d) to point (e) in FIG. 5. The
refrigerant is further expanded and decompressed by the second flow
control device 10b, and turns into a low-temperature and
low-pressure, two-phase gas-liquid state. The change of the
refrigerant at this time is represented by a vertical line
extending from point (e) to point (f) in FIG. 5.
The low-temperature and low-pressure refrigerant in the two-phase
gas-liquid state that has flowed out of the second flow control
device 10b flows into the second intermediate heat exchanger 9b.
Then, the refrigerant is heated while cooling brine, and turns into
a low-temperature and low-pressure gas refrigerant. The change of
the refrigerant at the second intermediate heat exchanger 9b is
represented by a slightly-slanted substantially horizontal straight
line extending from point (f) to point (a) in FIG. 5, in view of
pressure loss. The low-temperature and low-pressure gas refrigerant
that has flowed out of the second intermediate heat exchanger 9b
passes through the fourth solenoid valve 11d and flows into the
second branch portion 8b. The low-temperature and low-pressure gas
refrigerant that has flowed into the second branch portion 8b
passes through the second refrigerant pipe 7 and the four-way valve
2, flows into the compressor 1, and is compressed.
The first flow control device 10a at this time may be controlled
such that the degree of subcooling of the refrigerant at the outlet
of the first intermediate heat exchanger 9a reaches a predetermined
value, and the second flow control device 10b can be set to be
fully opened. Furthermore, by installing a pressure gauge at the
third branch portion 8c, the fourth flow control device 12b may be
controlled such that the pressure at the third branch portion 8c
stays constant, the first flow control device 10a may be controlled
such that the degree of subcooling of the refrigerant at the outlet
of the first intermediate heat exchanger 9a reaches a predetermined
value, and the second flow control device 10b may be controlled
such that the degree of superheat of the refrigerant at the outlet
of the first intermediate heat exchanger 9a stays constant.
Next, the flow of brine will be explained. Since the indoor units C
and D are performing cooling and the indoor unit E is performing
heating, the switching valves 19e, 19f, 19g, 19k, 19l, and 19m for
brine are opened, and the switching valves 19c, 19d, 19h, 19i, 19j,
and 19n for brine are closed.
The brine heated by the refrigerant at the first intermediate heat
exchanger 9a is subjected to pressurization and driven by the first
pump 18a, and flows into the fourth branch portion 8d. The brine
that has flowed into the fourth branch portion 8d passes through
the switching valve 19e for brine and the first brine pipe 6e on
the indoor side, and flows into the indoor unit E. The brine heats
the indoor air at the indoor heat exchanger 5e, and heating is
performed. At the time of heating, the brine is cooled by the
indoor air, passes through the second brine pipe 7e on the indoor
side, and returns to the relay unit B. The brine flows into the
first intermediate heat exchanger 9a while being expanded and
decompressed by the flow control device 20e for brine.
In contrast, the brine cooled by the refrigerant at the second
intermediate heat exchanger 9b is subjected to pressurization and
driven by the second pump 18b, and flows into the fifth branch
portion 8e. The brine that has flowed into the fifth branch portion
8e passes through the switching valves 19f and 19g for brine and
the first brine pipes 6c and 6d on the indoor side, and flows into
the indoor units C and D. The brine cools the indoor air at the
indoor heat exchangers 5c and 5d, and cooling is performed. At the
time of cooling, the brine is heated by the indoor air, passes
through the second brine pipes 7c and 7d on the indoor side, and
returns to the relay unit B. The brine flows into the second
intermediate heat exchanger 9b while being expanded and
decompressed by the flow control devices 20c and 20d for brine.
[Heating Main Operation]
The case where the indoor unit C is performing cooling and the
indoor units D and E are performing heating will now be explained.
In this case, the four-way valve 2 is switched so that refrigerant
discharged from the compressor 1 is caused to flow into the first
branch portion 8a. The first solenoid valve 11a and the fourth
solenoid valve 11d are opened, and the second solenoid valve 11b
and the third solenoid valve 11c are closed. At this time, the
first intermediate heat exchanger 9a operates as a condenser and
the second intermediate heat exchanger 9b operates as an
evaporator. FIG. 6 is a P-h diagram illustrating the transition of
refrigerant in the heating main operation. The flow of refrigerant
will be explained first, and the flow of brine will be explained
next.
In this state, the operation of the compressor 1 starts. The
low-temperature and low-pressure gas refrigerant is compressed by
the compressor 1, and is discharged as a high-temperature and
high-pressure gas refrigerant. The refrigerant compression process
by the compressor is represented by a line extending from point (a)
to point (b) in FIG. 6.
The high-temperature and high-pressure gas refrigerant discharged
from the compressor 1 flows into the first branch portion 8a
through the four-way valve 2 and the first refrigerant pipe 6. The
high-temperature and high-pressure gas refrigerant that has flowed
into the first branch portion 8a passes through the first branch
portion 8a and the first solenoid valve 11a, and flows into the
first intermediate heat exchanger 9a. Then, the refrigerant is
cooled while heating brine, and turns into an
intermediate-temperature and high-pressure liquid refrigerant. The
change of the refrigerant at the first intermediate heat exchanger
9a is represented by a slightly-slanted substantially horizontal
straight line extending from point (b) to point (c) in FIG. 6.
The refrigerant that has flowed out of the first intermediate heat
exchanger 9a is expanded and decompressed by the first flow control
device 10a and the second flow control device 10b. The change of
the refrigerant at this time is represented by a vertical line
extending from point (c) to point (d) in FIG. 6. The
low-temperature and low-pressure refrigerant in the two-phase
gas-liquid state that has flowed out of the second flow control
device 10b flows into the second intermediate heat exchanger 9b.
The refrigerant is heated while cooling brine by a heating quantity
necessary for an indoor unit, and turns into a low-temperature and
low-pressure refrigerant. The change of the refrigerant at the
second intermediate heat exchanger 9b is represented by a
slightly-slanted substantially horizontal straight line extending
from point (d) to point (e) in FIG. 6, in view of pressure
loss.
The low-temperature and low-pressure refrigerant that has flowed
out of the second intermediate heat exchanger 9b passes through the
second refrigerant pipe 7, flows into the heat-source-side heat
exchanger 3, is heated while cooling the outdoor air, and turns
into a low-temperature and low-pressure gas refrigerant. The change
of the refrigerant at the heat-source-side heat exchanger 3 is
represented by a slightly-slanted substantially horizontal straight
line extending from point (e) to point (a) in FIG. 6. The
low-temperature and low-pressure gas refrigerant that has flowed
out of the heat-source-side heat exchanger 3 passes through the
four-way valve 2, flows into the compressor 1, and is
compressed.
The first flow control device 10a at this time may be controlled
such that the degree of subcooling of the refrigerant at the outlet
of the first intermediate heat exchanger 9a reaches a predetermined
value, and the second flow control device 10b can be set to be
fully opened. Furthermore, as illustrated in FIG. 7, for example,
by operating the fourth flow control device 12b so that the
pressure at the third branch portion 8c stays constant, causing the
liquid refrigerant to be split at the third branch portion 8c,
controlling the first flow control device 10a so that the degree of
subcooling of the refrigerant at the outlet of the first
intermediate heat exchanger 9a reaches a predetermined value, and
controlling the second flow control device 10b so that the degree
of superheat of the refrigerant at the outlet of the first
intermediate heat exchanger 9a reaches a predetermined value, the
flow rate of the refrigerant flowing into the second intermediate
heat exchanger 9b can be adjusted, thereby enabling load adjustment
to be smoothly performed.
In FIG. 7, point (f) represents the state of the refrigerant at the
outlet of the second intermediate heat exchanger 9b, point (g)
represents the state of the refrigerant that has flowed out of the
fourth flow control device 12b, and point (e) represents the state
after the refrigerant at point (f) and the refrigerant at point (g)
merge together at the first branch portion. FIG. 7 is a P-h diagram
illustrating another example of the transition of refrigerant in
the heating main operation.
The flow of brine is substantially the same as that in the
explanation of the flow of brine in the cooling main operation, and
only connection of the indoor unit D is changed from the second
intermediate heat exchanger 9b to the first intermediate heat
exchanger 9a. Therefore, an explanation of the flow of brine will
be omitted.
In the air-conditioning apparatus 100, the heat source unit A
includes the control means 50, the relay unit B includes the
control means 51, and the indoor units C to E include the control
means 52c to 52e, respectively. In this configuration, the control
means is installed in each of the heat source unit A, the relay
unit B, and the indoor units C to E. However, there will be no
problem if control means is integrated into one unit and actuators
are controlled by communicating control values among individual
units. In the explanation provided below, the control means 50, 51,
and 52c to 52e will sometimes be collectively referred to as
control means.
The control means 52c to 52e perform driving control, such as
operation, stopping, and the like of fan motors for the fans 5c-m
to 5e-m on the basis of the settings of remote control for the
indoor units C to E and the current indoor temperature. As
described above, the control means 51 performs setting of the
opening degree of flow control devices, switching of solenoid
valves, and driving of pumps in the relay unit B, in accordance
with the operation mode based on the operation capacity for cooling
and heating of the indoor units C to E. In contrast, the control
means 50 performs driving of the compressor 1, switching of the
four-way valve 2, and driving control of the fan motor for the fan
3-m.
Hereinafter, a method for driving the compressor 1 and the fan
motor for the fan 3-m will be discussed. The compressor 1 and the
fan motor for the fan 3-m are controlled, for example, as described
in Patent Literature 1, on the basis of the pressure gauges 31 and
32 attached to the input and output channels of the compressor 1,
so that a fixed target pressure is reached. In the case where
discharge pressure cannot be controlled during a cooling main
operation, connection of the four-way valve 2 is switched. In the
case where suction pressure cannot be controlled during a heating
main operation, connection of the four-way valve 2 is switched.
Accordingly, the operation mode is switched between the cooling
main operation and the heating main operation. Here, there is a
possibility that the capacities of the intermediate heat exchangers
9a and 9b may not be continuous with respect to a change in the
number of operating indoor units among the indoor units C to E
during a cooling and heating simultaneous operation and, therefore,
the required heat exchange amount in one of the intermediate heat
exchangers 9a and 9b may be increased.
In this explanation, two intermediate heat exchangers are provided
for three indoor units. However, assuming that a plurality of
small-capacity indoor units are connected, for example, in a
cooling main operation based on an indoor capacity of 90 percent on
cooling and 10 percent on heating, although load is reduced by only
10 percent compared to the case of 100 percent on cooling, the
capacity of an intermediate heat exchanger for cooling is halved,
thus increasing the load of the intermediate heat exchanger. Thus,
during the cooling main operation, control is performed such that
the evaporating temperature is set low by reducing the suction
pressure at the compressor 1. The same applies to the relationship
between a heating operation and a heating main operation.
FIG. 8 illustrates a control flow at the time of a cooling main
operation. FIG. 8 is a flowchart illustrating the flow of a control
process at the time of a cooling main operation of the
air-conditioning apparatus 100. Here, the case where each type of
control is performed by the control means 50, 51, and 52c to 52e
communicating with each other will be explained as an example.
In S1, the control means starts operation control. In S2, since,
typically, the evaporating temperature of a refrigeration cycle
needs to be about 10 degrees Centigrade to perform cooling and the
condensing temperature needs to be about 40 to 50 degrees
Centigrade to perform heating, the control means sets an initial
value ETm0 of a target value for the evaporating temperature and an
initial value CTm0 of a target value for the condensing temperature
by taking pressure loss of refrigerant generated in the interval
from the heat source unit A to the relay unit B into consideration
for the above values. Since a change in the capacity of the
intermediate heat exchangers 9a and 9b is not continuous with
respect to a change in the capacity of the indoor units C to E, the
cooling load may be increased with respect to the capacity of the
intermediate heat exchanger 9b operating as an evaporator during a
cooling main operation.
Thus, in S3, the control means performs the following operation. In
the case of expression (1) provided below, where At is the heat
transfer area of the intermediate heat exchangers 9a and 9b at the
time of a cooling operation, Arc is the heat transfer area of the
intermediate heat exchanger 9b operating as an evaporator at the
time of a cooling main operation, Qct is the rated load of cooling,
and Qc is the current cooling load, it is determined that the load
of the intermediate heat exchanger 9b operating as an evaporator is
increased compared to the time of a cooling rated operation, and a
change amount .DELTA.Etm in the target value for the evaporating
temperature is calculated. Qc>Qct.times.(Arc/At) Expression
(1)
Since the heat exchange amount is determined based on the product
of the heat transfer area, the heat transfer coefficient, and the
difference in temperature between fluids that perform heat
exchange, on the assumption that the heat transfer coefficient is
constant, the log-mean temperature difference between brine and
refrigerant can be set to increase by the reciprocal of the cooling
load ratio (Qc/Qct) and the reduction (Ar/At) in the heat transfer
area, and the evaporating temperature can be set to reduce. This is
represented by expression (2) provided below.
.DELTA.ETm=(1-(Qc/Qct)/(Ar/At)).times.dTc, Expression (2)
where dTc represents the log-mean temperature difference between
refrigerant and brine at the time of a rated operation in an
intermediate heat exchanger. Furthermore, by taking into
consideration an improvement in heat transfer coefficient due to
increases in flow rate of refrigerant and brine, control
appropriate for the load can be achieved.
In S4, the control means updates the target value Etm for the
evaporating temperature. In S5, the control means converts the
target values for the evaporating temperature and the condensing
temperature into pressures according to the physical property of
refrigerant. In S6, the control means controls the frequency of the
compressor 1 and the capacity of the heat-source-side heat
exchanger 3 so that the discharge and suction pressures reach the
target values.
FIG. 9 illustrates a control method in a heating main operation.
FIG. 9 is a flowchart illustrating the flow of a control process at
the time of a heating main operation of the air-conditioning
apparatus 100. Here, the case where each type of control is
performed by the control means 50, 51, and 52c to 52e communicating
with each other will be exemplified. Thus, the control means 50,
51, and 52c to 52e will be collectively referred to as control
means.
Control regarding S9 to S16 in the heating main operation is
similar to that in the cooling main operation, and a change amount
.DELTA.Ctm of the target value for the condensing temperature may
be calculated using expression (3) provided below.
.DELTA.CTm=((Qh/Qht)/(Arh/At)-1).times.dTh, Expression (3)
where Qh is the current heating load, Qht is the rated load of
heating, Arh represents the heat transfer area of a condenser at
the time of a heating main operation, At represents the heat
transfer area of the intermediate heat exchanger 9a at the time of
a heating operation, and dTh represents the log-mean temperature
difference between refrigerant and brine at the time of a rated
operation in an intermediate heat exchanger.
In an air-conditioning apparatus 100 capable of a cooling and
heating simultaneous operation with the configuration described
above, operation is performed such that the control target value
for the compressor suction pressure at the time of a cooling main
operation is set equal to or lower than that at the time of a
cooling operation and the control target value for the compressor
discharge pressure at the time of a heating main operation is set
equal to or higher than that at the time of a heating operation,
thereby improving the efficiency and increasing the heating
capacity in the individual operation modes.
Furthermore, .DELTA.ETm may be determined based on the capacity of
the first pump 18a of a brine circuit for cooling, and .DELTA.CTm
may be determined based on the capacity of the second pump 18b of a
brine circuit for heating. When the capacity of a pump has reached
100 percent, it is determined that the conveyance power of the pump
is insufficient, the target value for the difference in temperature
between outlet and inlet of brine is increased, that is, the
required flow rate is reduced to lower the load of the pump. At the
same time, when a pump for cooling has reached 100 percent,
.DELTA.ETm is set so that ETm is reduced, and when a pump for
heating has reached 100 percent, .DELTA.CTm is set so that CTm is
increased. With this operation, the load is adjusted at the
compressor. This method makes it possible to improve the efficiency
and increase the heating capacity, irrespective of the indoor
temperature and load.
Furthermore, in the case where the capacity of a pump has reached
100 percent or the opening degree of any of the valves of the flow
control devices 20c to 20e has reached a maximum opening degree,
there is a possibility that control appropriate for the capacity of
the flow control devices 20c to 20e for the indoor units cannot be
performed. Thus, the flow rate of brine is reduced, and the target
value for the difference in temperature between outlet and inlet of
brine is increased to enable flow control. When the target value
for the difference in temperature between outlet and inlet of brine
is increased, it is determined that the required capacity is
increased, and .DELTA.ETm and .DELTA.CTm may be determined in such
a manner that ET is reduced and CT is increased to interlock with
control of a water circuit.
As described above, the air-conditioning apparatus 100 according to
Embodiment 1 is controlled such that the first intermediate heat
exchanger 9a and the second intermediate heat exchanger 9b each
operate as an evaporator during a cooling operation, the first
intermediate heat exchanger 9a operates as a condenser and the
second intermediate heat exchanger 9b operates as an evaporator
during a cooling main operation, and thus the number of
intermediate heat exchangers operating as evaporators at the time
of the cooling operation is greater than in the cooling main
operation. In addition, control is performed such that the first
intermediate heat exchanger 9a and the second intermediate heat
exchanger 9b each operate as a condenser during a heating
operation, the first intermediate heat exchanger 9a operates as a
condenser and the second intermediate heat exchanger 9b operates as
an evaporator during a heating main operation, and thus the number
of intermediate heat exchangers operating as condensers at the time
of the heating operation is greater than in the heating main
operation. Furthermore, operation is performed in such a manner
that the control target value for the compressor suction pressure
at the time of a cooling main operation is set equal to or lower
than that at the time of a cooling operation, and a control target
value for the compressor discharge pressure at the time of a
heating main operation is set equal to or higher than that at the
time of a heating operation, thereby improving the efficiency and
increasing the heating capacity in the individual operation modes.
Therefore, with the air-conditioning apparatus 100, even if the
load conditions change, the cooling and heating capacities are
maintained, and operation in a state where the efficiency of cycle,
such as COP, is high can be achieved.
Embodiment 2
FIG. 10 is a schematic circuit configuration diagram illustrating
an example of a refrigerant circuit configuration of an
air-conditioning apparatus 200 according to Embodiment 2 of the
present invention. The air-conditioning apparatus 200 will be
explained with reference to FIG. 10. In Embodiment 2, differences
from Embodiment 1 will be mainly explained and explanation of the
same portions as those in Embodiment 1, such as a refrigerant
circuit configuration, will be omitted. Furthermore, since each
operation mode executed by the air-conditioning apparatus 200 is
similar to that performed by the air-conditioning apparatus 100
according to Embodiment 1, an explanation of the operation mode
executed by the air-conditioning apparatus 200 will be omitted.
The heat transfer areas of the intermediate heat exchangers 9a and
9b within the relay unit B of the air-conditioning apparatus 200
are different from those of the air-conditioning apparatus 100
illustrated in FIGS. 1 and 2. For example, by setting the heat
transfer area of the intermediate heat exchanger 9b to the heat
transfer area of the intermediate heat exchanger 9a to 2:1, an
intermediate heat exchanger 9b having a larger heat transfer area
can be used as an evaporator and an intermediate heat exchanger 9a
having a smaller heat transfer area can be used as a condenser
during a cooling main operation, and an intermediate heat exchanger
9b having a larger heat transfer area can be used as a condenser
and an intermediate heat exchanger 9a having a smaller heat
transfer area can be used as an evaporator during a heating main
operation. With this configuration, the ratio of the heat exchange
capacities of the intermediate heat exchangers can be made closer
to the load ratio of the indoor units C to E, thereby efficiently
improving the capacity of a cooling and heating simultaneous
operation. Since the control method is similar to that in
Embodiment 1, an explanation of the control method will be
omitted.
As described above, with the air-conditioning apparatus 200
according to Embodiment 2, operation is performed in such a manner
that the control target value for the compressor suction pressure
at the time of a cooling main operation is set equal to or lower
than that at the time of a cooling operation and the control target
value for the compressor discharge pressure at the time of a
heating main operation is set equal to or higher than that at the
time of a heating operation, thereby improving the efficiency and
increasing the heating capacity in the individual operation modes.
Therefore, similar to the air-conditioning apparatus 100 according
to Embodiment 1, with the air-conditioning apparatus 200, even if
the load conditions change, the cooling and heating capacities can
be maintained, and operation in a state where the efficiency of
cycle, such as COP, is high can be achieved.
Embodiment 3
FIG. 11 is a schematic circuit configuration diagram illustrating
an example of a refrigerant circuit configuration of an
air-conditioning apparatus 300 according to Embodiment 3 of the
present invention. The air-conditioning apparatus 300 will be
explained with reference to FIG. 11. In Embodiment 2, differences
from Embodiment 1 described above will be mainly explained and an
explanation of the same portions as those in Embodiment 1, such as
a refrigerant circuit configuration, will be omitted. Furthermore,
since each operation mode executed by the air-conditioning
apparatus 300 is similar to that executed by the air-conditioning
apparatus 100 according to Embodiment 1, an explanation of the
operation mode will be omitted.
The air-conditioning apparatus 300 is different from the
air-conditioning apparatus 100 illustrated in FIGS. 1 and 2 in that
the number of pipes connecting the heat source unit A and the relay
unit B together is changed from 2 into 3. In the air-conditioning
apparatus 300, a third refrigerant pipe 22 is installed so that a
discharge pipe of the compressor 1 in the heat source unit A and
the first branch portion 8a in the relay unit B are connected
together. In the air-conditioning apparatus 300, the first
refrigerant pipe 6 is connected to the third branch portion 8c, and
a fifth flow control device 23 for adjusting the flow rate of
refrigerant flowing into the heat-source-side heat exchanger 3 is
installed between the heat-source-side heat exchanger 3 and the
first refrigerant pipe 6. The air-conditioning apparatus 300 is
different from the air-conditioning apparatus 100 in that in the
case where there is an indoor unit performing heating, a
refrigerant discharged from the compressor 1 passes through the
third refrigerant pipe 22 and is supplied to the intermediate heat
exchangers 9a and 9b.
Furthermore, in the case where the heat-source-side heat exchanger
3 operates as a condenser, a thermometer is installed between the
heat-source-side heat exchanger 3 and the fifth flow control device
23, and the fifth flow control device 23 is controlled such that,
for example, the degree of subcooling stays constant based on the
difference from the condensing temperature calculated from the
discharge pressure of the compressor 1, and in the case where the
heat-source-side heat exchanger 3 operates as an evaporator, a
thermometer is installed between the heat-source-side heat
exchanger 3 and the four-way valve 2, and the fifth flow control
device 23 is controlled such that, for example, the degree of
superheat stays constant based on the difference from the
evaporating temperature calculated from the suction pressure of the
compressor 1. The other flow of refrigerant is substantially the
same as the flow explained using FIGS. 3 to 7 in Embodiment 1.
Therefore, an explanation of the flow will be omitted.
Furthermore, since control is performed in the same way as in
Embodiment 1, an explanation thereof will be omitted. With the
configuration described above, by controlling the compressor
suction pressure at the time of a cooling and heating simultaneous
operation to be lower than that at the time of a cooling operation
and controlling the discharge pressure at the time of the cooling
and heating simultaneous operation to be lower than that at the
time of a heating operation as in Embodiments 1 and 2, operation
can be performed in a high-efficiency state during a cooling
operation and a heating operation, and at the same time, the
cooling and heating capacities may be maintained high during a
cooling and heating simultaneous operation.
As described above, with the air-conditioning apparatus 300
according to Embodiment 3, operation is performed in such a manner
that the control target value for the compressor suction pressure
at the time of a cooling main operation is set equal to or lower
than that at the time of a cooling operation and the control target
value for the compressor discharge pressure at the time of a
heating main operation is set equal to or higher than that at the
time of a heating operation, thereby improving the efficiency and
increasing the heating capacity in the individual operation modes.
Thus, with the air-conditioning apparatus 300, similar to the
air-conditioning apparatus 100 according to Embodiment 1, even if
the load conditions change, the cooling and heating capacities can
be maintained, and operation in the state where the efficiency of
cycle, such as a COP, is high can be achieved.
Although the cases where three indoor units are provided have been
explained in Embodiments 1 to 3 as examples, any number of indoor
units may be connected. In addition, the cases where two
intermediate heat exchangers are provided have been explained as
example. However, obviously, the number of intermediate heat
exchangers provided is not necessarily two. Any number of
intermediate heat exchangers may be provided as long as the
intermediate heat exchangers are configured to be capable of
cooling and/or heating a heat medium and as long as control is
performed such that the number of intermediate heat exchangers
operating as evaporators during a cooling operation is greater than
the number of intermediate heat exchangers operating as evaporators
during a cooling main operation and that the number of intermediate
heat exchangers operating as condensers during a heating operation
is greater than the number of intermediate heat exchangers
operating as condensers during a heating main operation.
Furthermore, since the distribution performance of a heat exchanger
decreases as the flow rate of refrigerant decreases, control may be
performed such that a given upper limit value is specified for the
number of intermediate heat exchangers to operate as condensers or
condensers in accordance with the load of indoor units.
Furthermore, each of the number of the first pumps 18a provided and
the number of the second pumps 18b provided is not necessarily one.
A plurality of small-capacity pumps may be connected in series or
in parallel. Furthermore, although the cases where the accumulator
4 is included have been explained in Embodiments 1 to 3, the
accumulator 4 is not necessarily provided.
REFERENCE SIGNS LIST
1: compressor, 2: four-way valve, 3: heat-source-side heat
exchanger, 3-m: flow control device (fan), 4: accumulator, 5:
indoor heat exchanger, 5c: indoor heat exchanger, 5d: indoor heat
exchanger, 5e: indoor heat exchanger, 5-m: flow control device
(fan), 5c-m: fan, 5d-m: fan, 5c-m: fan, 6: first refrigerant pipe,
6c: first brine pipe, 6d: first brine pipe, 6e: first brine pipe,
7: second refrigerant pipe, 7c: second brine pipe, 7c: second brine
pipe, 7d: second brine pipe, 7e: second brine pipe, 8a: first
branch portion, 8b: second branch portion, 8c: third branch
portion, 8d: fourth branch portion, 8e: fifth branch portion, 8f:
sixth branch portion, 8g: seventh branch portion, 9a: intermediate
heat exchanger, 9b: intermediate heat exchanger, 10a: first flow
control device, 10b: second flow control device, 11a: first
solenoid valve, 11b: second solenoid valve, 11c: third solenoid
valve, 11d: fourth solenoid valve, 12a: third flow control device,
12b: fourth flow control device, 13: refrigerant-refrigerant heat
exchanger, 14: check valve, 15: check valve, 16: check valve, 17:
check valve, 18a: first pump, 18b: second pump, 19c: switching
valve, 19d: switching valve, 19e: switching valve, 19f: switching
valve, 19g: switching valve, 19h: switching valve, 19i: switching
valve, 19j: switching valve, 19k: switching valve, 19l: switching
valve, 19m: switching valve, 19n: switching valve, 20c: flow
control device: 20d: flow control device, 20e: flow control device,
21a: flow passage switching valve, 21b: flow passage switching
valve, 22: third refrigerant pipe, 23: fifth flow control device,
31: pressure gauge, 32: pressure gauge, 33a: thermometer, 33b:
thermometer, 33c: thermometer, 33d: thermometer, 33e: thermometer,
34a: thermometer, 34b: thermometer, 34c: thermometer, 34d:
thermometer, 34e: thermometer, 41: thermometer, 42c: thermometer,
42d: thermometer, 42e: thermometer, 50: control means, 51: control
means, 52c: control means, 52d: control means, 52e: control means,
52c: control means, 52d: control device, 60a: first connecting
pipe, 60b: second connecting pipe, 100: air-conditioning apparatus,
200: air-conditioning apparatus, 300: air-conditioning apparatus,
A: heat source unit, B: relay unit, C: indoor unit, D: indoor unit,
E: indoor unit.
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